层状岩质斜坡层厚变化规律及机理研究
首发时间:2018-05-28
摘要:以黄河上游某水电站层状岩体斜坡为对象,首先,通过90个勘探平硐和地表大量变质砂岩和板岩层厚的现场测量和统计,揭示层厚的空间变化规律;然后,结合地质环境及其演化,分析岩层薄化的影响因素及影响范围;最后,基于地应力测量、岩体波速测试、三轴应力-弹性波耦合试验和数值计算,探讨卸荷作用下陡倾层状岩体斜坡的岩层薄化机理。结果表明:岩层薄化是岩性、构造、卸荷和风化等因素综合作用的结果,软硬相间岩层及其潜在弱面是岩层薄化的基础,构造作用使潜在弱面剪切,卸荷作用使潜在弱面显性张裂,风化使地表岩层进一步变薄。河流下切使软硬相间陡立层状岩体斜坡内的地应力场非常复杂,坡顶和坡面岩层内潜在弱面直接拉张,斜坡内一定深度范围内岩层沿潜在弱面发生压致拉裂,斜坡内陡立层状岩体发生大范围岩层薄化。受之影响,层状岩体斜坡内层厚总体上随深度增加振荡式增加并在一定深度达到原生厚度而趋于稳定,层间错动带、褶皱带、卸荷裂隙带附近的层厚普遍较薄并也随埋深增大而增加,岩层厚度及影响范围随高程增加而增加,左岸反倾岩层的厚度和影响范围大于右岸顺倾岩层。层厚、埋深、纵波速度和应力状态之间具有较好的相关性,表明层厚始终储存于地应力状态。研究成果为层状岩体工程中力学性质与变形破坏研究和工程设计提供基础。
关键词: 地质工程 层状岩体 岩层厚度 岩层薄化 地应力场 卸荷
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Study on Rules and Mechanism of Layer Thickness Variation in Stratified Rock Slope
Abstract:IFirstly, the slope of stratified rock mass of a hydropower station in the upper reachesof the Yellow River was takenas an object, and the spatial variation laws of layer thickness ofmetamorphic sandstones and slatewas revealed through field measurementin 90 adits and on the ground.Then, combining with the geological environment and its evolution, the influencing factors and the influence scope of layer thinning were analyzed.Finally, based on in-situ stress measurements, rock mass wave velocity tests, stress-elastic wave coupling triaxial tests and numerical simulations, the mechanism of layer thinning in steeply inclined stratified rock mass slopes under unloading conditions was researched.The combined effects of lithology, geotectonic movement, unloading, and weathering lead to the thinning of rock layer.The soft-hard interbedded rock mass and their potential weak planes are the foundationof thelayer thinning. The geotectonic movements make the potential weak planesto shear andthen the action of unloadingdrives the surfaces to open into cracks. Afterwards, the action of weathering causes the shallow rocks further thinning.River incisionmakes the stress field in the rock slope very complicated, which leads to the potential weak planes within the slopecrest and the slope develop into tension cracks. Meanwhile, the compression fracture along the potential weak planes also happenedwithin a certain depth range of the slope, and thenlayer thinning occurred in a wide range of the steeply stratified rock slope.As a result, the thickness of layer in the stratified rock mass generally increases oscillatingly with depth,andit will tend to stable values where the thickness reaches the thickness of theoriginalstrata.Moreover, the layer thickness near the bedding fault zone, in the fold belts, and near the unloading crack belts are generally thinnerbut alsorise with the increase of burial depth. The layerthickness and its influence range increase with increasing elevation,andit is greaterin the anti-dip stratum in the left flank than in the right flank.In addition, there is a positive correlation among layer thickness, depth of burial, p-wave velocity and geo-stress, which indicates that the layer thickness is always influenced by in-situ stress state.This research can providesreferences for the study of mechanical properties and deformation failure and for the design of rock engineeringin the stratified rock mass.
Keywords: geological engineering stratified rock mass layer thickness of rock layer thinning of rock geo-stress field unloading
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